Roller chopping effects on tamaulipan scrub community composition

Abstract

Palatability of shrub sprouts to white-tailed deer (Odocoileus virginianus Raf.) differs among species, which causes selective browsing and can shift shrub species composition to dominance by less palatable species. The hypothesis was tested that differences in palatability of new sprouts among shrub species following roller chopping small (4 ha) patches within a shrubland matrix would result in a shift in shrub species composition within the patches toward less palatable species. Relative density and relative canopy cover of all woody species in plots 9 years after 1 roller chopping treatment, in plots 3 years after 2 roller chopping treatments, and in untreated plots were estimated. Relative density of blackbrush acacia (Acacia rigidula Benth.) was 3 times greater and relative canopy cover was 12 times greater 9 years after the first roller chopping treatment compared to untreated plots, but relative density and relative canopy cover of blackbrush acacia in roller chopped plots were similar to relative density and relative canopy cover in untreated plots 3 years after the second roller chopping treatment. Relative canopy cover of spiny hackberry (Celtis pallida Torr.) in plots roller chopped in 1989 and 1995 was higher than in untreated plots. Relative density and canopy cover of all other species were similar between roller chopped and untreated plots. Shrub community composition 9 years after 1 roller chopping treatment or 3 years after 2 roller chopping treatments in the subtropical thornscrub communities in southern Texas did not shift toward greater dominance of less palatable species.